Aqueous two-component polyurethane coating composition, process for its preparation, and its use in processes for the production of a multicoat finish

An aqueous two-component polyurethane coating composition, comprising

• an aqueous dispersion of a polyacrylate resin having an OH number of from 40 to 200 mg of KOH/g, an acid number of from 20 to 100 mg of KOH/g, and a glass transition temperature of from -40.degree. C. to +60.degree. C.;
• and
• a polyisocyanate component as crosslinking agent;
• wherein the polyacrylate resin comprises, as polymerized monomer units,
• a1) one or more esters selected from the group consisting of esters of acrylic acid, esters of methacrylic acid, and mixtures thereof;
• a2) one or more ethylenically unsaturated monomers having at least one hydroxyl group per molecule;
• a3) optionally one or more vinyl esters of .alpha.-branched monocarboxylic acids having 5 to 18 carbon atoms per molecule, a4) optionally at least one compound selected from the group consisting of reaction products of acrylic acid, methacrylic acid, and mixtures thereof with glycidyl esters of .alpha.-branched monocarboxylic acids having 5 to 18 carbon atoms per molecule, wherein said reaction products may be formed prior to, during, or after polymerization of the polyacrylate resin;
• a5) one or more ethylenically unsaturated monomers having at least one carboxyl group per molecule;
• and
• a6) optionally one or more additional ethylenically unsaturated monomers;
• and further wherein at least one of (a3) and (a4) is included in the polyacrylate resin;
• and yet further wherein the monomers of (a1), (a2), (a3), (a4), (a5), and (a6) are all different and copolymerizable with one another, and the monomers of (a1), (a2), and (a6) are substantially free of carboxyl groups.